This invention relates to reactant gas manifolds for fuel cell stacks having an initial convex shape which distorts when bolted to the fuel cell stack to provide a substantially uniform seal pressure along the length of the manifold.
Fuel cell stacks which utilize gaseous reactants conventionally are provided with opposed pairs of external manifolds which distribute the reactant gases to the cells in the stack, and which gather reactant exhaust gases from the cells in the stack. In the larger commercial stacks, the manifolds may take the form of large shells which abut the sides of the stack and are secured in place by some sort of fastening means. U.S. Pat. No. 4,345,009 is illustrative of such a commercial stack and manifold construction.
When this type of construction is used, care must be taken to seal the edges of the manifold against the stack so that the reactant gases and the exhaust gases will not escape into the ambient surroundings. This seal has been effected with elastomeric gaskets and also with elastomeric adhesive gaskets. The elastomeric gaskets rely on the compression forces of the mechanism which secures the manifold to the stack for their integrity. The elastomeric adhesive gaskets provide a more stable seal because they rely on compressive forces plus adhesion to the stack and to the manifold for their integrity.
Common practice has been to provide fuel cell manifolds with extremely flat sealing surfaces. However, even when elastomeric adhesive gaskets are employed, complex load retention systems are still required to obtain uniform pressure along the length of the manifold seal.
Objects of the invention include: provision of a fuel cell reactant gas manifold which inherently provides a more uniform pressure along the length of the seal between the manifold and the fuel cell stack; a fuel cell reactant gas manifold which simplifies manufacture and assembly and reduces cost of producing fuel cells; and a fuel cell stack having better seals between the stack and the reactant gas manifolds.
According to the present invention, a manifold for reactant gases of a fuel cell stack is produced with a convex sealing surface in at least one dimension; distortion of the manifold when bolted to the fuel cell stack straightening the convex surfaces and providing a substantially uniform pressure seal along the length of the manifold-stack interface. The invention is particularly suited for use where it is difficult or impossible to establish a bolt line along the seal.
Other objects, features and advantages of the present invention will become more apparent in the light of the following detailed description of exemplary embodiments thereof, as illustrated in the accompanying drawing.